This invention relates generally to bearings, and more particularly to bearings having an alternative load path for extreme loads.
Recently, wind turbines have received increased attention as environmentally safe and relatively inexpensive alternative energy sources. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
Generally, a wind turbine includes a rotor having multiple blades. The rotor is mounted to a housing or nacelle, which is positioned on top of a truss or tubular tower. Utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., 30 or more meters in diameter). Blades on these rotors transform wind energy into a rotational torque or force that drives one or more generators that may be rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert mechanical energy to electrical energy, which is fed into a utility grid.
Wind turbines including direct drive generators eliminate the gearbox, and reliability problems associated with the gearboxes. However, in at least some known wind turbines, rotor bearings, pitch bearings, generator bearings and other bearings may prematurely fail. Because the bearings can be difficult to access and replace, failure of bearings can result in a lengthy and expensive repair process.
To facilitate reducing costs while optimizing turbine availability, bearing replacement and/or repair should be performed rapidly at the wind turbine site with a minimal infrastructure and skill set required. However, known bearings used in wind turbines generally require change-out at the factory or labor intensive and costly on-site repair.